Meghan Markle's former Suits costars have revealed the advice they gave her when they learned she was dating Prince Harry way before the rest of the world.

The show's stars Rick Hoffman, Sarah Rafferty and Gina Torres - who have all scored invites to the big day - opened up for the first time ever about the royal romance, revealing she confided in them in the early days of the relationship.

"I had gotten the news early, and I was like, 'you got to be kidding me,'" Rick - who plays Louis Litt - said in a chat with Today on Friday.

"And it was like, both of us in the trailer like, 'oh, my. You're going - you're dating a prince?'"

But once the news set in, he gave his former co-star some age words of advice.

"We knew she was excited. And there was reason to keep it, you know, close to the vest," she explained.

Naturally all three were pumped as badgers when they found out they'd been invited to the royal shindig at Windsor - even if they didn't make it to the guestlist for the reception.

The Suits cast became 'family' (Image: NBCUniversal)

"You hope, as we all do, the best for her. This is an incredible step in her life. To bear witness to that is extraordinary," said Gina.

And recalling what a top kind of gal Meghan is, Rick shared an example of when she proved to be a stand-up chum.

"I was in a relationship that didn't work out. I had to go to a wedding in Paris five years ago to this weekend. It was in Paris and I didn't have a date, I was dateless. And Meghan said to me, "do you want me to come with you?"' he recalled.